1. Field of the Invention
The invention relates to armor. More specifically, the invention relates to fiber reinforced composite armor.
2. Background
In recent years, fragment-resistant materials formed from high tensile strength fibers such as aramid fabrics or polyethylene fabrics have gone into common use. These fragment resistant materials typically have the advantages of greater tensile strength and the less weight per unit area then metals.
High-tensile strength fibers such as, for example, aramid fibers in fabrics have been combined with polymer matrices to form polymer-polymer composite armor. These fiber reinforced polymer matrices benefit from the high-tensile strength of the aramid fabric and high resistance to fracture and fatigue of the polymer matrix. Multiple layers of high tensile strength aramid fabric can be combined with epoxy matrices, and compacted into an armor shield or housing.
High performance engines, for example, in airplanes or helicopters, frequently have high performance turbines that spin at very high velocities. The tremendous energy imparted to these turbines can suddenly be released by a catastrophic event. A catastrophic event may occur when, for example, a turbine fails and breaks apart due to fatigue. A fragment of the failed turbine, released from its anchor on the turbine shaft, will have its angular momentum converted into velocity and hit the turbine housing with tremendous force.
A turbine housing designed to withstand such a failure and resist penetration of the fractured turbine part before it causes injury will need to have high fragmentation projectile resistance. A turbine housing designed to withstand such a failure in a helicopter engine will require high fragmentation projectile resistance and lightweight. A turbine housing designed to withstand such a failure in an armor vehicle or boat engine where adequate air circulation is not available will require high fragmentation projectile resistance and an ability to operate at high temperatures.
A simulation for a fragmentation test based more directly on the particular threat involved is the xe2x80x9csimulated fragmentation test.xe2x80x9d A projectile is made out of, for example, a tri-lobed compressor wheel, which is fashioned, from high-hardened steel or a titanium composite. The tri-lobed compressor wheel is cut into pieces, each of which is turned into a projectile. The projectile is loaded into a sabot round and fired out of the 76 mm smooth bore cannon. This simulated fragmentation test is a more specific threat simulation and applies more closely to armor designed for a turbine housing. Existing turbine housings are capable of withstanding up to about 10,000 foot pounds of force as measured by the above mentioned xe2x80x9csimulated fragmentation testxe2x80x9d before failing.